References (or refs or simply reliable sources), on Wikipedia, are important to verify content and inform the reader of its source. Any editor can remove unsupported statements if they cannot be verified in a reliable source reference they can add to the article, and unsubstantiated articles may be deleted if no reliable sources coverage can be found. When adding content to an article, cite your sources to help readers verify facts or find more details. It is also useful to update or improve existing references.

Good references

A citation must verify the statement in the text. To verify the statement "Mike Brown climbed Mt. Everest", you cannot rely on a general reference about Mt. Everest or a reference on Mike Brown. You need to cite a source that directly supports the statement about his achievement. Wikipedia does not publish original research (e.g. your own unpublished, or self-published, essay or research).

When you are not sure whether a source is reliable, ask other editors on the reliable sources noticeboard. Before posting, check the list of perennial sources and search the archives on the noticeboard to see if the source you want to cite has already been discussed.

If the reference source is a lengthy book, paper, or article, you should give specific chapter, section, or page numbers if possible.